Smart-Responsive Colloidal Capsules as an Emerging Tool to Design a Multifunctional Lubricant Additive

Abstract

The microencapsulation technique has been proven as a powerful and flexible tool to design and develop a multifunctional additive for various applications. The significant characteristics of this technique center around the ability to control the release of the core active ingredients by tuning the porosity and the permeability of the shell. However, this original concept has faced a major roadblock in lubricant research since it causes a major breakage of the microcapsules (∼70%) under severe stressed-shearing conditions. The shell fragments generated from such unwanted events significantly influence the friction and wear performances of the counterpart, thus limiting the ongoing research of the microencapsulation technique in tribology. To solve such technical bottlenecks, we develop a new strategy of utilizing the microencapsulation technique which focuses on the smart responsiveness of the shell with the base lubricant and the synergy between the incorporated materials. In this study, the smart-responsive colloidal capsule has been developed based on our proposed concept that demonstrates outstanding performances in improving the lubricity of the conventional melt lubricant (by ∼70%) under hot metal working conditions. An unprecedented oxidation–reduction (by ∼93%) and the first instance of ultralow friction (0.07) at elevated temperatures (880 °C) have been initially achieved. This work opens a new avenue of customizing a multifunctional additive package by utilizing the smart colloidal capsules in lubrication science.

Synergistic and Competitive Effects between Zinc Dialkyldithiophosphates and Modern Generation of Additives in Engine Oil

“…In practice, many additives have been proven to have synergistic effects on each other when they were combined in a lubricant package [26,27]. Nevertheless, there are also a lot of additive combinations which exhibit competitive effects and reduce the functional quality of the lubricant fluid [28,29].…”

Insight into the Mechanical Behavior of Hybrid Colloidal Capsules at Elevated Temperatures by Direct Visualization of the Interfacial Solid-State Reactions

“…Hybrid colloidal capsules have been intensively applied in various research areas including self-healing materials, anticorrosion coatings, self-lubricating coatings, smart lubricants, , and biomedical delivery systems . This kind of material has been increasingly applied in improving energy efficiency, delivering the safety requirements, and ensuring the reliability of the working components at high temperatures.…”

Thermoresponsive Hybrid Colloidal Capsules as an Inorganic Additive for Fire-Resistant Silicone-Based Coatings

“…Due to the hydrophobic nature of stearic acid, the nanoparticles were preferably deposited at the water–oil interfaces and stabilized the water-in-oil emulsion system. It has been found that the concentration of the nanoparticles in the solution, as the stabilizing agent, plays an important role in the formation of the intact colloidal capsules . The effect of nanoparticle concentration and the water-in-oil (w/o) ratio on the formation of the colloidal capsules is displayed in Figure .…”

“…Microencapsulation has recently been recognized as an effective method for fire-retardant and fire-resistant innovative solutions . This technique not only allows an ability to protect the sensitive compounds, e.g., organic flame retardants, but also combines several functional fillers in a single platform . In addition, the synergistic effect between the materials in the microcapsule can be achieved, which significantly reduces the overall additive content in the formulation while attaining an acceptable level of fire performance .…”

“…21 This technique not only allows an ability to protect the sensitive compounds, e.g., organic flame retardants, but also combines several functional fillers in a single platform. 22 In addition, the synergistic effect between the materials in the microcapsule can be achieved, which significantly reduces the overall additive content in the formulation while attaining an acceptable level of fire performance. 21 The most popular feature for core−shell structures comes from the shell materials which can be adjusted for tunable permeability, 23 environmental response, 24 and external stimulus triggers.…”